Q:

In racquetball, a "crotch shot" is defined as when the ball hits two surfaces (eg walls,floor) simultanteously. When hitting the front wall + floor "crotch" simultaneously, can the ball approach from any angle or does it have to be at 45 degrees?

- Jay (age 62)

Fairfax, VA, USA

- Jay (age 62)

Fairfax, VA, USA

A:

Hello Jay,

This is a pretty interesting question.

If we only consider the ideal situation, i.e. the racquetball is incompressible and assuming the surface of wall and floor forms a degree of 90, then the answer is yes-it has to approach at exactly 45^{o}. The reason is that if we look at the moment when the ball touches both surfaces simultaneously, we see two perpendicular surfaces tangent to the sphere, which forces the center of our racquetball to be at exactly 45^{o} incident angle. [Whoops, see below- that doesn't mean that before contact it also had to be at 45° angle. Our goof.]

But in reality, a racquetball is never a perfectly incompressible sphere. Thus, when you hit the racquetball to the corner, though not at 45^{o}, it is still possible that the ball hits one surface first, then gets compressed and hits the other surface while still in contact with both. Thus, in this case, it doesn't necessary have to be at 45^{o}.

Hope this helps,

Lingyi

*(published on 02/09/2013)*

Q:

Your answer assumes that both the front wall and the floor are struck equally hard by the uncompressible ball. Isn't it true that if you place the ball in the crotch of the wall and you can see it from anywhere (at any angle) on the court, then it is theoretically possible to have hit the ball to that exact spot from where you are standing? In which case, you can hit the crotch of the wall/floor from virtually ANY angle, yes?

- Jay Wald (age 62)

Fairfax, VA 22033

- Jay Wald (age 62)

Fairfax, VA 22033

A:

You're absolutely right. And you've picked out the incorrect hidden assumption of our old answer.

Mike W.

*(published on 09/22/2013)*